//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//

// UNSUPPORTED: c++03, c++11, c++14

// <numeric>

// Became constexpr in C++20
// template <class InputIterator1, class T,
//           class BinaryOperation, class UnaryOperation>
//    T transform_reduce(InputIterator1 first1, InputIterator1 last1,
//                       T init, BinaryOperation binary_op, UnaryOperation unary_op);
//

#include <numeric>
#include <cassert>
#include <utility>
#include <iterator>

#include "test_macros.h"
#include "MoveOnly.h"
#include "test_iterators.h"

struct identity
{
    template <class T>
    constexpr decltype(auto) operator()(T&& x) const {
        return std::forward<T>(x);
    }
};

struct twice
{
    template <class T>
    constexpr auto operator()(const T& x) const {
        return 2 * x;
    }
};

template <class Iter1, class T, class BOp, class UOp>
TEST_CONSTEXPR_CXX20 void
test(Iter1 first1, Iter1 last1, T init, BOp bOp, UOp uOp, T x)
{
    static_assert( std::is_same_v<T,
                    decltype(std::transform_reduce(first1, last1, init, bOp, uOp))> );
    assert(std::transform_reduce(first1, last1, init, bOp, uOp) == x);
}

template <class Iter>
TEST_CONSTEXPR_CXX20 void
test()
{
    int ia[]          = {1, 2, 3, 4, 5, 6};
    unsigned sa = sizeof(ia) / sizeof(ia[0]);

    test(Iter(ia), Iter(ia),    0, std::plus<>(),       identity(),       0);
    test(Iter(ia), Iter(ia),    1, std::multiplies<>(), identity(),       1);
    test(Iter(ia), Iter(ia+1),  0, std::multiplies<>(), identity(),       0);
    test(Iter(ia), Iter(ia+1),  2, std::plus<>(),       identity(),       3);
    test(Iter(ia), Iter(ia+2),  0, std::plus<>(),       identity(),       3);
    test(Iter(ia), Iter(ia+2),  3, std::multiplies<>(), identity(),       6);
    test(Iter(ia), Iter(ia+sa), 4, std::multiplies<>(), identity(),    2880);
    test(Iter(ia), Iter(ia+sa), 4, std::plus<>(),       identity(),      25);

    test(Iter(ia), Iter(ia),    0, std::plus<>(),       twice(),       0);
    test(Iter(ia), Iter(ia),    1, std::multiplies<>(), twice(),       1);
    test(Iter(ia), Iter(ia+1),  0, std::multiplies<>(), twice(),       0);
    test(Iter(ia), Iter(ia+1),  2, std::plus<>(),       twice(),       4);
    test(Iter(ia), Iter(ia+2),  0, std::plus<>(),       twice(),       6);
    test(Iter(ia), Iter(ia+2),  3, std::multiplies<>(), twice(),      24);
    test(Iter(ia), Iter(ia+sa), 4, std::multiplies<>(), twice(),  184320); // 64 * 2880
    test(Iter(ia), Iter(ia+sa), 4, std::plus<>(),       twice(),      46);
}

template <typename T, typename Init>
TEST_CONSTEXPR_CXX20 void
test_return_type()
{
    T *p = nullptr;
    static_assert( std::is_same_v<Init,
         decltype(std::transform_reduce(p, p, Init{}, std::plus<>(), identity()))> );
}

TEST_CONSTEXPR_CXX20 void
test_move_only_types()
{
    MoveOnly ia[] = {{1}, {2}, {3}};
    assert(60 ==
        std::transform_reduce(std::begin(ia), std::end(ia), MoveOnly{0},
        [](const MoveOnly& lhs, const MoveOnly& rhs) { return MoveOnly{lhs.get() + rhs.get()}; },
        [](const MoveOnly& target) { return MoveOnly{target.get() * 10}; }).get());
}

TEST_CONSTEXPR_CXX20 bool
test()
{
    test_return_type<char, int>();
    test_return_type<int, int>();
    test_return_type<int, unsigned long>();
    test_return_type<float, int>();
    test_return_type<short, float>();
    test_return_type<double, char>();
    test_return_type<char, double>();

//  All the iterator categories
    test<cpp17_input_iterator        <const int*> >();
    test<forward_iterator      <const int*> >();
    test<bidirectional_iterator<const int*> >();
    test<random_access_iterator<const int*> >();
    test<const int*>();
    test<      int*>();

//  Make sure the math is done using the correct type
    {
    auto v = {1, 2, 3, 4, 5, 6};
    unsigned res = std::transform_reduce(v.begin(), v.end(), 1U, std::multiplies<>(), twice());
    assert(res == 46080);       // 6! * 64 will not fit into a char
    }

    test_move_only_types();

    return true;
}

int main(int, char**)
{
    test();
#if TEST_STD_VER > 17
    static_assert(test());
#endif
    return 0;
}
